TAG 166 - Geological Society of Australia

Feature 1Feature 1Snowy Mountains Hydroelectric SchemeAt the 34th International Geological Conference (IGC) inBrisbane last August, I presented a lecture on the SnowyMountains Scheme. This fostered some interest among myengineering geology colleagues and I plan to publish a paper on it indue course. This article provides a brief summary of the project and thehuge legacy it has provided the geotechnical profession.The Snowy’s contribution toengineering geologyThroughout the 1950s and 1960s I was aware of this great scheme whilegrowing up in Canberra. With my family I would visit the Snowy Mountainsfor skiing and bushwalking and for trips to see the large dams.While a student at ANU I was also privileged to attend a field trip led byDavid Stapledon, one of the first engineering geologists to work on theconstruction. It was probably this trip that inspired me to follow a careerin this field.The Snowy Mountains Scheme, often known simply as the ‘Snowy’,was constructed from 1949 to 1974 and is located in southeast NewSouth Wales, about 100 km from Canberra. The high country forms adivide between three main catchment areas for the Snowy, Murray andMurrumbidgee Rivers. Broadly, the scheme was devised to transferwaters from the Snowy River to the inland for irrigation purposes, withthe combined benefit of generating hydroelectricity.The project is in two sections:l northern — Snowy–Tumut developmentl southern — Snowy–Murray development.Both developments are connected by tunnels to a mainregulating storage on the Eucumbene River. The completed schemecomprises 16 large dams, over 145 km of tunnels and seven powerstations with an installed generating capacity of 3756 MW.The area was first surveyed in the mid-19th Century and the conceptof diverting water inland can be traced back to the 1880s. However, itwas not until 1949 that the Snowy Mountains Hydro-electric Power Act1949 was enacted, after much deliberation between the bordering statesof Victoria and New South Wales. This was a large ‘Plan for the Nation’and the Snowy Mountains Hydro-Electric Authority (SMHEA) wasset-up under the leadership of the indefatigable Sir William Hudson. Hebrought together a team of world specialists to undertake this challenge.After World War II there were many displaced people, including skilledprofessional and trades people who also made the move to Australiato start a new life and take up the challenge in the remote SnowyMountains. The construction period was from 1949 to 1974, startingwith the Guthega Dam in 1951, well above the snow line.The engineering challenges were immense in the remote and ruggedmountains, with steeply incised river valleys and extensive snow coverin winter. The decision to construct underground powerhouses was partlydue to the tough climatic conditions and partly to reasons of nationaldefence. The Snowy Mountains Scheme is clearly the largest hydroelectricdevelopment in Australia and at the time of construction wasone of the largest development projects in the world.An information sign at one of the key locations for the Scheme — a familiarsite for visitors to the area up to the 1970s. Image courtesy SMEC collection.Inspection of the Jindabyne Dam site in 1951. The chief of the SnowyMountains Commission, Sir William Hudson, in the grey coat, is with DanielMoye on his left. From Dan Moye collection at http://www.daniel-moye.org.Geology of the areaThe Snowy Mountains are a set of high plateaus dominated by granitesand metamorphics of the Lachlan Foldbelt. Generally the area hasOrdovician metamorphosed sedimentary rocks that have been intrudedby Silurian to Devonian granites with some development of gneisses. Onthe northern flanks are Devonian volcanic and sedimentary rocks, thena capping of remnants of Cenozoic basalt lava flows. Also of significanceare the Quaternary to Holocene lacustrine and alluvial deposits, inaddition to one of the few areas of glacial formations in the main range.The geological structure comprises prominent north–southfoliation, with extensive normal and strike-slip faulting thatdeveloped prior to and during uplift in the Cenozoic.The geomorphological history is complex and has beeninherited from one of fault-scarp development, crustal uplift and warping.This has resulted in stream capture, such as where the upper Murrumbidgeeused to flow south to the Snowy River catchment, and nowforms a significant about-turn to the north and then west.22 |TAG March 2013